1. Field of Invention
The present invention relates to fuel level measurement and more particularly, to the measurement and calculation of fuel level in tanks of electrical generators and run time estimation for the generators.
2. Discussion of Related Art
As known to those skilled in the art, typical engine driven generator sets with sub base tanks and/or with separate fuel tanks have relatively crude methods for detecting and reporting fuel level. One well-known type of device used with such fuel tanks is a float gauge that provides a visual indication such as “E-¼-½-¾-F”. It is also known to use level switches set, for example, at 50% and 25% levels to provide low fuel warnings and shut down of a generator. With many generator sets, and in particular diesel generator sets, it is desirable to shut down the generator prior to fuel starvation to prevent engine damage and what can be a laborious task of bleeding air out of a fuel injection system before being able to restart the generator. More advanced fuel measurement systems are available that provide finer resolution in ½ inch to 1 inch increments, and other systems are available that use, for example, voltage dividing sensors that have even higher linear resolutions.
Typical problems with the more advanced systems include the cost of these systems, and further, these systems are often implemented in a conservative manner to prevent shutdown or fuel starvation. Often, shutdown will occur when a tank is as much as 25% full, because of concern of tolerances in the system, and because the exact location of the fuel pickup tube in the tank relative to the sensor is not known with any precision. Many fuel sensors are mounted to the top of the tank, with the lowest reading (i.e. “empty”) located at a distance from the bottom of the tank. This can result in an “empty” reading while there is still fuel remaining in the tank. Further, when a fuel tank is located on ground that is not level, a reading at the sensor location may not be indicative of the level of the tank at the location of the fuel pickup tube.
Premature warnings of an impending empty tank can cause a critical system to be shut down early and/or a call for a refill of the tank to be made sooner than necessary.
During the operation of typical generators it is often difficult to determine how much remaining run time is available before refilling of the fuel tank is required. This is caused by inaccuracies in fuel sensors used, lack of fine resolution in the fuel sensors and variability of power draw of loads.